Examples of a recording technology using physical properties of a chalcogenide material include a phase-change memory and a phase-change optical disk. As an example of a phase-change material used for the phase-change memory and the phase-change optical disk, a chalcogenide material containing Te (tellurium) has been known. The properties of this chalcogenide material differ depending on its composition. In Japanese Journal of Applied Physics, Vol. 43, 2004, pp. 4704-4712 (Non-Patent Document 2), in view of crystallization mechanisms of phase-change materials used in general, the materials are broadly classified into two types, that is, a crystal nucleation type and a crystal growth type.
In the phase-change optical disk, laser light is irradiated to heat the chalcogenide material, thereby causing a phase change between amorphous and crystalline phases for recording. The reading of recorded information is performed using a difference in reflectivity between an amorphous state and a crystalline state. Japanese Patent Application Laid-Open Publication No. 8-127176 (Patent Document 2) discloses that at least one element X selected from the group including Cr, Ag, Ba, Co, Ni, Pt, Si, Sr, Au, Cd, Cu, Li, Mo, Mn, Zn, Al, Fe, Pb, Na, Cs, Ga, Pd, Bi, Sn, Ti, V, In, and lanthanoid elements is added to a Ge—Sb—Te-based phase-change recording film. Such a specific element X is added for the purpose of, for example, preventing fluidity of the recording film and improving the number of rewritable times.
Also, U.S. Pat. No. 5,254,382 (Patent Document 3) discloses an optical disk medium using a chalcogenide material represented by {(GeyTe1-y)a(SbzTe1-z)1-a}1-b(In1-xTex)b (where 0.4≦y≦0.6, 0.3≦z≦0.6, 0.4≦x≦0.6, 0.1≦a≦0.5, 0.01≦b≦0.3) as a recording layer. In this optical disk medium, In is added to Ge—Sb—Te for the purpose of increasing the stability of an amorphous state to improve the long storability of data, while maintaining the properties of being able to be crystallized at high speed.
On the other hand, U.S. Pat. No. 5,883,827 (Patent Document 1) and IEEE International Electron Devices meeting, TECHNICAL DIGEST, 2001, pp. 803-806 (Non-Patent Document 1) disclose details of a non-volatile memory using a chalcogenide-material film. This non-volatile memory is a phase-change memory in which storage information is written by the change of the atomic arrangement in the phase-change material film in accordance with the Joule heat and cooling rate resulting from the current flowing through the phase-change material film itself. For example, when transformed into an amorphous phase, since a heat higher than 600° C. is applied to the phase-change material film by the Joule heat so as to once melt the phase-change material film, the operation current tends to be increased, and the resistance value changes as much as two to three orders of magnitude depending on the situation.
Of the electric phase-change memories, those using Ge2Sb2Te5 have been mainly studied. For example, Japanese Patent Application Laid-Open Publication No. 2002-109797 (Patent Document 4) discloses a recording element using GeSbTe. Also, Japanese Patent Application Laid-Open Publication No. 2003-100991 (Patent Document 5) discloses a technology regarding a memory using a chalcogenide material. Furthermore, Nature Materials, Vol. 4, 2005, pp. 347-351 (Non-Patent Document 3) discloses a technology regarding a phase-change memory using a crystal-growth-type material.    Patent Document 1: U.S. Pat. No. 5,883,827    Patent Document 2: Japanese Patent Application Laid-Open Publication No. 8-127176    Patent Document 3: U.S. Pat. No. 5,254,382    Patent Document 4: Japanese Patent Application Laid-Open Publication No. 2002-109797    Patent Document 5: Japanese Patent Application Laid-Open Publication No. 2003-100991    Non-Patent Document 1: IEEE International Electron Devices meeting, TECHNICAL DIGEST, 2001, pp. 803-806    Non-Patent Document 2: Japanese Journal of Applied Physics, Vol. 43, 2004, pp. 4704-4712    Non-Patent Document 3: Nature Materials, Vol. 4, 2005, pp. 347-351